Abstract
Soybean phytase was extracted with 2% CaCl2 and partially purified by ammonium sulphate fractionation followed by dialysis in 0.01 M tris-maleate buffer, pH 6.5. The enzyme showed an optimum pH of 4.8 and optimum temperature of 60°C. The phytase was partially inhibited at high substrate concentration, with an optimum substrate concentration at 20 mM and a Km value of 2.4 × 10-3 M. Vmax was 0.22 μmole Pi liberated/min/mL enzyme. The inactivation and activation energies for the hydrolysis of phytic acid were approximately 47,000 cal/mole and 11,100 cal/mole, respectively. Enzyme activity was inhibited by about 25%, 23% and 22% in the presence of 10-3 M Zn++, Cu++ and Hg++, respectively, and was also decreased by about 85% in the presence of 10-1 M N-ethylmaleimide and sodium fluoride. Reducing and chelating agents at concentrations up to 10-1 M inhibited activity by about 50% and by more than 90%, respectively.
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